Given the wide deployment of Outlook Express however, I expect it
alone is sufficient to ensure the continuation of this convention,
ceteris paribus.
With that same justification we could blame almost any misfeature of the
current mail system on Outlook Express.
The half-life of a windows system before it's upgraded, reinstalled, or
retired is what, two or three years? Even Outlook Express can change,
and people tend to install new software or even buy new hardware when their
current systems succumb to bitrot.
Given that users are going to replace or upgrade what they have sooner
or later, what should that replacement or upgrade do differently than
current software does?